MULTIYEAR OBSERVATIONS OF ORGANOHALOGEN PESTICIDES IN THE ARCTIC ATMOSPHERE

Atmospheric measurements of organohalogen pesticides (OCs) have been m ade in both the Canadian and Russian Arctic. A full quality-controlled database of weekly samples is now available for the years 1992-94. He xachlorobenzene (HCB) and the hexachlorocyclohexanes (HCHs) were the m ost predominant compounds in the atmosphere, followed by the chlordane s and endosulfan. Evidence of a seasonality in air concentrations was apparent particularly for the pesticide metabolites, compounds such as oxy-chlordane, heptachlor epoxide and dieldrin showing a significant positive correlation with temperature (p<0.01). An exception to this w as p, p'-DDE which showed elevated levels during the winter. Large spa tial differences in mean annual concentrations of most OCs were not ev ident; however, spatial differences were apparent in alpha/gamma-HCH r atios between the high Arctic site of Alert and the Yukon site of Tagi sh. The influence of both the European sector and the regional effect of the Arctic Ocean on the high Arctic probably accounted for this dif ference. A decline in the trans-chlordane/cis-chlordane ratio compared to studies during the 1980s may indicate a more weathered source of c hlordane to be present in the Arctic by the mid-1990s. Slopes generate d from plots of partial pressure (In P) versus 1/T for selected compou nds were considerably less steep than those derived from temperate stu dies. It is inferred here that long-range transport has a large influe nce on contaminant levels in the arctic atmosphere. (C) 1998 Elsevier Science Ltd. All rights reserved.